Vaporizer for two-stage liquefied petroleum gas dispensing systems



Oct. 12, 1948. WHITE;

VAPORIZER FOR TWO-STAGE LIQUEFIED PETROLEUM GAS DISPENSING SYSTEMS Filed Dec. 28, 1944' INKENTOR. L. J Win ze.

ATTORNEY,

l atented Get. 12, 1948 VAPORIZER PETROLEUM GAS DI FOR TWO-STAGE LIQUEFIED SPENSING SYSTEMS Loyd J. White, San Antonio, Tex., assignor to Southern Steel a corporation of Texas 1 Application December 28, 1944, Serial No. 570,170

2 Claims.

This invention relates to liquefied petroleum gas dispensing systems, wherein a mixture of liquefied gases, such as butane and propane, is stored in a pressure storage tank and vapor is generated by discharging liquid from the tank through a, first-stage pressure reducing regulator into a heat exchanger utilizing the liquid fuel as the heating medium, the generated vapor being delivered from the vaporizer through a secondstage pressure regulator for use in consuming appliances. One of the objects of the invention is to provide a new type of vaporizer, utilizing a segregated portion of the fuel contents of the tank to supply the latent heat of vaporization to the residual liquid which passes through the firststage regulator. In this respect, the invention involves important improvements in the type of system disclosed in my application Serial No. 237,113, filed October 26, 1938. The main idea is to provide a new type of two-stage pressure reducing, liquid eduction system, wherein liquefied gas in the storage tank is circulated rapidly through a heat exchanger or tank to supply the latent heat of vaporization for the educted liquid. A further and most important aim is to provide an internal vaporizer in the storage tank so constructed and arranged as to provide for complete submergence of the vaporizer in the liquid fuel and thereby insure complete vaporization under normal loads until practically all of the liquid fuel is exhausted from the tank.

Other aims and advantages of the invention will appear in the following description when considered in connection with the accompanying drawing, wherein the figure is a sectional view, partly in elevation, showing a two-stage liquid eduction system embodying the invention.

The improved system is especially contrived to supply liquefied petroleum gas of a uniform B. t .u. content from a mixture of butane and propane. The new vaporizer is shown as being applied to an underground system of the general type disclosed in the aforesaid co-pending application. The fuel usually consists of a mixture composed principally of butane including upwards of twenty per cent propane. If the fuel is vaporized by the batch method, it is subject to weathering and causes trouble, due to variation in the heating value of the gas. This invention, therefore, applies to a two-stage liquid eduction system, wherein the fuel is vaporized between two regulators.

Referring more particularly to the drawing, the invention is applied to an underground system employing a pressure storage tank II), which Company, San Antonio, Tex.,

- is buried in heat exchange relation with the surrounding earth. It is shown as being provided with a single riser or stand-pipe II to which is connected a composite valved fitting [2, through which the tank is adapted to be filled. Such a fitting is generally disclosed in my Patent No. 2,176,829, and needs no further description. The stand-pipe and the fitting are arranged within at protecting casing or housing I3 extending above the ground level, so that the fitting is easily accessible from above the ground.

The tank is shown as being partially filled with liquefied petroleum gas which is maintained under pressure, the vapor pressure being dependent upon the temperature and the particular mixture employed, ranging between, say, tewnty pounds to fifty pounds per square inch, gauge. In this example, a heat exchanging tank I4, which may be made of relatively thin sheet metal, is shown as being arranged within the tank Ill in the vapor space, so that it is not exposed to heat exchange with the liquid in the main tank. It may be secured to the top portion of the storage tank by welding, as shown, or by any other convenient securing means. Spaced depending pipes I5 and i6 are shown as being connected to the bottom portion of the tank I4 and extending to a point near the bottom of the storage tank, so that liquid fuel may be withdrawn from the storage tank and circulated through the heat e chan e as will presently be explained. An outlet tube or conduit I! is shown as being connected to communicate with the top portion of the tank l4 so that liquid or gas, as the case may be, will be withdrawn. The liquid then passes through a first-stage, pressure reducing regulator I8 of the usual type, which reduces the pressure from, say, about forty pounds down to five or ten pounds per square inch. The liquid is partially vaporized, due to its contained heat, as it passes through this first-stage, pressure reducing regulator and the mixture of vapor and residual liquid is delivered through a tube I9 and a heat exchanger or vaporizing coil 20 within the heat exchanging tank l4; thence, through an outlet tube 21, through the valve fitting I2 and an ordinary second-stage regulator 22 connected thereto, which reduces the pressure to the desired service pressure of about six ounces. The gas then passes through the usual service pipe 23 and is delivered to the consuming appliances It will be noted that the heat exchanging tank or compartment I4 is relatively small in comparison with the capacity of the main tank Ill. The arrangement is such that, when gas is being con- 3 sumed, the vapor pressure within the heat exchanging tank is reduced, thereby permitting liquid to rush into the vaporizing tank, due to the superior vapor pressure existing in the storage tank. The vaporizing tank is promptly filled with liquid because only a slight pressure reduction will be sufficient to cause the liquid; tQrise-in,

the two pipes l5 and 16. It will be understood that mixtures of butane and propane have a specific gravity of five tenths or Iessdepending upon the amount of propane in the mixture and, since storage tanks are usually not more than'two or three feet in diameter, pressurev redllQtion; of only. a few ounces will be sufficient to causev the liquid, to rush into the heat exchanging tank and keep it full.

The liquefied fuel, which fills the heat exchanging tank, supplies the sensible heat or latent heat of vaporization for the residual liquid discharged through the, first-stage, pressure reducting regulator |8. The arrangementofuthe-coil;. is such that its coldest portion or intake end is above the depending tube or pipe I E-and the. outletend, which is the warmest portion, is above the depending tube or pipe l5. Due to this arrangement, the liquid is thermo-syphon-ically circulated very rapidly through the heat exchanging tank, thecoldest liquid naturally settling; or circulating downwardly very rapidly as. it is chilled. The greater the demand for fuel, the greater will be therate of circulation. of the liquid in heat exchanging contact with the coil Zll. Furthermore,

the arrangement is such that the coil will be completely submerged in the liquid fuel, thereby in.- suring complete vaporization thereof, as long as there is any fuel in the storage tank. This evercomes one of the great difiiculties encountered in connection with systems employing coils or vaporizing chambers submerged in the body of liquid within the tank. When they are exposed to heat exchanging contact with the vapor inthe tank, the rate of heat transfer is considerably. diminished. and is some times insufiicient to in.- sure vaporization of the residual, liquid between the pressure reducing regulators, especially, when the demand reaches a maximum.

In the operation of the system, the heat exchanging tank will. be filledwith gas at the same; vapor pressure as that in the storage tank when no gas is being consumed. In other words, the

liquid levels in the two tanks will be equalized However, as soon as there is a gas demand by. the consuming appliances, suchas cookstoves, water heaters and thelike, the supply. of trapped gas in the heat exchanging tank or chamber will;

quickly be exhausted and replaced by liquid fuel, due to the reduction in vapor pressure. The liquid fuel will fill the heat exchanging-tank and keep it liquid full as long. as there is any substantial demand for gas by the consuming appliances, thus insuring completevaporization of the residual liquid in the heat exchangingcoil.

From the foregoing description, it will be.-un-

derstood that this invention provides a very simeduction systems which insures uniform heat exchanging contact with the heat exchanging coilv as long as there is any fuel available in the system. Moreover, the heat exchanger can easily be installed in; a, tank and it can lie-made of very thin sheet, metal; because the. pr ssure,- difference between the vapor or liquid in the small tank and the main tank will be quite small.

Obviously, the present invention is not limited to the particular. embodiment thereof herein shown and described.

What is claimed is;

1. In. a liquefied petroleum gas dispensing'systern of the character described, an underground pressurestorage tank adapted to be charged with a mixture of liquefied gases; a heat exchanging chamber, in the form of a small tank arranged in the vapor space of said storage tank; a pair Qfspace depen ingpi esconnectedto the c ambe and emmu ica i g with. the bottom. p tio of; he sto aee a k; anduction pipe, c nnected o: the pp r. portion-of. the cham er nd. carry-- ing' a firstestage, pressure reducing regulator; a

vaporizing coil within. the chamber connected to,

the eduction pipe to receive the educted. fuel; passing through. said regulator; eduction pipe extending throughthe upper portion ofsaid stor age tank at spaced. points and servingto hold said. small tank in, place; a vapor, outlet conduit,

connected to the coil; and a second=stage pres? sure reducingigegulator connected. to, said. vapor de ive c d it.

2. In. a liquefied petroleum. gas. dispensing sys- T tem ofthe character described,a pressure storage tankadapted to. be buried. underground and to be charged; With a mixture of. liquefied gases; a

cylindrical. heat exchanging chamber suspendedwithin; the gas space in, said. tank; spaced, dea pending pipes. connected to said. chamber: and! communicating; with the bottom. portion of said.

tank; an, eduction tube connected to. the upperportion of saidchamber and extending outside! v ofssaidtank; afirstestage, pressure reducingregulator connected to saideduction. tube; said. educ tion tubaex-tending through-theupper portion of the tank at spaced. points to. hold. the. chamber in place; a vaporizing coil within the chamber I and connected. to; receiv eductedfuel from said regulator; avapor; delivering conduit leadingfromj saidcoilto the point of use; and a second-stage pressure reducing regulator connected to said.

' vapor delivering conduit.

LOYD J.

REFERENCES. CITED.

The. following references are of records in. the file of this patent:

UNITED.- s'rArites PATENTS Garretson. June 12, 1 .145; 

